1. Field of the Invention
The present invention generally relates to semiconductor devices having a built-in contact-type sensor and, more particularly, to a semiconductor device packaged with a built-in contact-type sensor element being exposed on a surface thereof.
Along with the popularization of electronic information communication, a demand of performing individual recognition in electronic equipments is increasing so as to protect the confidentiality of personal information. Various techniques have been developed as individual recognition means, and, among them, a fingerprint distinguishing technique has attracted attention. A semiconductor device into which a contact-type sensor using electrostatic capacity is incorporated has been developed as a small device used for distinguishing a fingerprint.
2. Description of the Related Art
Generally, a fingerprint sensor referred to as a capacitance-type recognizes a fingerprint by having a fingertip directly contact a sensor surface. A fingerprint sensor referred to as a sweep-type reads a fingerprint image by sweeping a sensor surface with a finger. The sweep-type fingerprint sensor is capable of recognizing a fingerprint image by sweeping with a finger even a small width for example, about 1 mm. Accordingly, the sweep-type has become popular as a fingerprint sensor to be incorporated into portable equipment.
The electrostatic-capacity sensor used as a fingerprint sensor can be formed on a silicon substrate like a semiconductor device. That is, a fingerprint sensor can be manufactured as a part of a semiconductor chip made by a silicon substrate.
FIG. 1 is a cross-sectional view of a conventional sweep-type fingerprint sensor apparatus 1. A semiconductor chip 3 in which a sensor part 2 as a fingerprint sensor is formed is mounted on a package substrate 5 through a die bonding material 4. The sensor part 2 is exposed in a part of a circuit forming surface 3a of the semiconductor chip 3. An electrode pad 6 is formed on the circuit forming surface 3a, and pads 9 that are electrically connected to the external connection terminals (solder balls) 7 are formed on the package substrate 5. Electrode pads 6 of the semiconductor chip 3 are wire-bonded to the pads 9 of the package substrate 5 by gold wires 10. The semiconductor chip 3 and the gold wires 10 are encapsulated by a seal resin 11 on the package substrate 5.
In the fingerprint sensor apparatus 1 of the above-mentioned structure, the sensor part 2 of the semiconductor chip 3 is a part onto which a finger is contacted directly, and, thus, the sensor part 2 must be exposed on the front surface of the fingerprint sensor apparatus 1. For this reason, the encapsulation of the semiconductor chip 3 is carried out so that the sensor part 2 is not covered by the seal resin 11. However, the electrode pads 6 are provided on the circuit forming surface 3a of the semiconductor chip 3 and the gold wires 10 are connected to the electrode pads 6, such a portion must be encapsulated by the seal resin 11. Therefore, in parts other than the part in which the sensor part 2 is exposed, a certain thickness is required for the seal resin 11 so as to cover the gold wires 10. That is, a certain height is needed from the exposed surface of the sensor part 2.
As mentioned above, the sensor part 2 is a part which is contacted directly by a finger, and, thus, it may become impossible to contact a finger completely if the surrounding part of the exposed part is high. In the case of a sweep-type fingerprint-sensor apparatus, since a width (in a direction X of FIG. 1) of the sensor part 2 is as small as about 1 mm, a finger may not completely contact if the surrounding part is high.
It is a general object of the present invention to provide an improved and useful semiconductor device having a built-in contact-type sensor in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device having a built-in contact-type sensor in which a height of a surrounding part of a sensor part from the exposed surface of the sensor part is reduced.
In order to achieve the above-mentioned object, there is provided according to the present invention a semiconductor device having a built-in contact-type sensor, comprising: a semiconductor element having a built-in sensor, the semiconductor element having a circuit forming surface and a back surface opposite to the circuit forming surface, the contact-type sensor and electrodes formed on the circuit forming surface, back electrodes formed on the back surface; conductive members extending through the semiconductor device from the electrodes to the back electrodes; a protective film covering the circuit forming surface in a state where a surface of the contact-type sensor is exposed; and external connection terminals electrically connected to the back electrodes.
According to the above-mentioned invention, the protective film covering the circuit forming surface cay be made very thin since there is no protruding part such as a bonding wire on the circuit forming surface. Thus, a height of a part surrounding a part where the contact-type sensor is exposed can be reduced. Thereby, a reliable contact on the exposed surface of the contact-type sensor can be made, which results in a reliable detection of the contact-type sensor.
In the semiconductor device according to the present invention, the conductive members may be formed by a conductive material filled in through holes. Accordingly, the electrodes on the side of the circuit forming surface can be easily connected to the back electrode on the side of the back surface by utilizing the through holes.
Additionally, an insulating protective film may be formed on the back surface of the semiconductor element, and the back electrode and the external connection terminals may be electrically connected to each other through patterned wires formed on the insulating protective film. Accordingly, the external connection terminals can be located at any positions by providing the patterned wires.
The semiconductor device according to the present invention may further comprise a semiconductor element for control which provides a function related to a sensor function of the semiconductor element having the built-in sensor, wherein the control semiconductor element for control being situated on a backside of the semiconductor element having the built-in sensor. Accordingly, the semiconductor element having the built-in sensor can be used exclusively for a sensor function, and a semiconductor element for controlling the sensor function can be separately produced. Thus, the semiconductor elements having each function can be effectively produced. Additionally, a projected area of the semiconductor elements can be reduced by providing the semiconductor elements for control under the semiconductor element having the built-in sensor.
In the semiconductor device according to the present invention, a plurality of the semiconductor elements may be provided which include the semiconductor elements for control which controls the sensor function of the semiconductor element having the built-in sensor and a semiconductor element for memory which stores data related to the sensor function. Accordingly, the semiconductor element for control can be produced separately as a semiconductor element for logic operations and a semiconductor element exclusive for memory. Thus, the semiconductor elements having each function can be efficiently produced. Additionally, a projected area of the semiconductor elements can be reduced by providing the semiconductor elements for control under the semiconductor element having the built-in sensor in a stacked state.
Additionally, the semiconductor element having the built-in sensor may be encapsulated in a state where the semiconductor element is mounted on the package substrate via the back electrodes so that the semiconductor device is formed as a ball grid array type semiconductor device. Accordingly, the ball grid array type semiconductor device having a built-in sensor can be easily produced by using the back electrodes.
Further, the semiconductor element having the built-in sensor may be encapsulated in a state where the semiconductor element is mounted on a lead frame, and the back electrodes may be electrically connected by bonding wires to lead terminals as the external connection terminals. Accordingly, the lead terminal type semiconductor device having a built-in sensor can be easily produced by using the back electrodes.
Additionally, in the semiconductor device according to the present invention, the contact-type sensor may be a fingerprint sensor of an electrostatic capacitance type. Accordingly, in the sweep-type fingerprint sensor in which a finger is moved while being brought into the sensor surface, a sweep operation of the finger can be reliably performed since a part surrounding the sensor surface is low, thereby reliable fingerprint detection or recognition can be carried out.
Additionally, there is provided according to another aspect of the present invention a manufacturing method of a semiconductor device having a built-in contact sensor, comprising the steps of: preparing a semiconductor element having a built-in sensor, the semiconductor element having a circuit forming surface and a back surface opposite to the circuit forming surface, the contact-type sensor and electrodes formed on the circuit forming surface; forming back electrodes on the back surface of the semiconductor element having the built-in sensor and forming through holes extending through the semiconductor element having the built-in sensor from the electrodes to the back electrodes; electrically connecting the electrodes to the back electrodes by filling a conductive material in the through holes; covering the circuit forming surface by a protective film in a state where a surface of the contact-type sensor is exposed; and forming external connection terminals on the back surface side so as to electrically connect the external connection terminals to the back electrodes.
According to the above-mentioned invention, the protective film covering the circuit forming surface cay be made very thin since there is no protruding part such as a bonding wire on the circuit forming surface. Thus, a height of a part surrounding a part where the contact-type sensor is exposed can be reduced. Thereby, a reliable contact on the exposed surface of the contact-type sensor can be made, which results in a reliable detection of the contact-type sensor.
The manufacturing method may further comprise the steps of: forming an insulating protective film on the back surface of the semiconductor element having the built-in sensor; forming patterned wires on the insulating protective film; and forming the external connection terminals at predetermined positions of the patterned wires. Accordingly, the external connection terminals can be located at any positions by providing the patterned wires.